1. 
Abstract—In this research, biodiesel wastes such as palm
shells (PS) and Jatropha curcas fruit shells (JS) were used for
the synthesis of activated carbon by chemical activation method
using potassium hydroxide (KOH) as an activating agent. The
effects of acidic treatment in hydrofluoric acid (HF),
impregnation ratio, activation temperature and activation time
on the adsorption capacity of methylene blue (MB) and iodine
(I2) solution were examined. The results showed that
HF-treated activated carbons exhibited high adsorption
capacities by eliminating ash residues, which might fill up the
pores. In addition, the adsorption capacities of methylene blue
and iodine solution were also significantly influenced by the
types of raw materials, the activation temperature and the
activation time. The highest adsorption capacity of methylene
blue of 257.07 mg/g and iodine of 847.58 mg/g were obtained
from Jatropha curcas wastes.
Index Terms—Activated carbon, biodiesel wastes, Jatropha
curcas fruit shells (JS), palm shells (PS).
I. INTRODUCTION
Activated carbons were usually prepared from organic
matter that consists of highly carbon. Agricultural wastes
were one of interesting choices because it is low cost,
renewable and abundant [1]–[3]. Palm shell (PS) and
Jatropha curcas fruit shell (JS) contain low nutrient, which is
not suitable for use as an agriculture fertilizer, but it is
abundant in cellulose, hemicelluloses and lignin resulting in
difficult to digest or degrade. Thus, a possible use of this
waste is converting it into value-added activated carbon,
which is one of the most widely used materials because of its
exceptional adsorbent properties [4]–[6].
In general, the process for preparation of activated carbons
involves two steps, carbonization of raw carbonaceous
materials in an inert atmosphere followed by the activation of
Manuscript received January 27, 2013; revised March 27, 2013. This
work was supported in part by the Department of Materials Science and
Engineering, Faculty of Engineering and Industrial Technology, Silpakorn
University.
Achanai Buasri, Nattawut Chaiyut, and Vorrada Loryuenyong are with
the Department of Materials Science and Engineering, Faculty of
Engineering and Industrial Technology, Silpakorn University, Nakhon
Pathom 73000 Thailand and the National Center of Excellence for Petroleum,
Petrochemicals and Advanced Materials, Chulalongkorn University,
Bangkok 10330 Thailand (e-mail: achanai130@hotmail.com,
nchaiyut@hotmail.com, vorrada@gmail.com).
Ekasit Phakdeepataraphan, Somchai Watpathomsub, and Vasin
Kunakemakorn are undergraduate students in bachelor's degree program
with the Department of Materials Science and Engineering, Faculty of
Engineering and Industrial Technology, Silpakorn University, Nakhon
Pathom 73000 Thailand (e-mail: man.ekasit@gmail.com,
senator0267@gmail.com, coaching_win@hotmail.com).
the carbonized product. The activation process can be
provided by two types, either by physical activation or
chemical activation. However, chemical activation is now
widely applied for the activation because of its lower
activation temperature and higher product yield compared
with the physical one [7].
The main objective of this work was to optimize the
processes for the synthesis of activated carbon from biodiesel
wastes (PS and JS) using carbonization and chemical
activation method. KOH was used as an activating agent and
the carbonization was performed under nitrogen atmosphere.
The effects of acidic treatment in hydrofluoric acid (HF),
impregnation ratio, activation temperature and activation
time on adsorption capacity of methylene blue (MB) and
iodine (I2) solution are systematically investigated.
II. EXPERIMENTAL METHODS
A. Materials and Preparation of Samples
Agricultural wastes (PS and JS) were supplied by
Research and Development Institute at Kamphaengsaen,
Thailand. The starting materials were first cleaned with water
and dried at room temperature for 24h. The dried samples
were crushed with a blender and sieved to a size 600-1,000
μm. The dried sample was then impregnated in KOH solution
(by weight ratio) at room temperature for 30 min. After that,
it was dried in a tube furnace at 1500
C for 2 h. The resulted
sample was further activated in a tube furnace at fixed
activation temperature and time. After cooling, the activated
carbon was washed several times with hot distilled water
until the pH became neutral. The washed sample was dried at
900
C for 24 h to obtain activated carbon of palm shells
(ACPS) and Jatropha curcas fruit shells (ACJS). Then the
obtained activated carbons were sieved to a size smaller than
150 μm as the final product.
B. Thermogravimetric Analysis (TGA)
The pyrolysis behaviors of PS and JS were determined on
a thermal analyzer (Perkin-Elmer, USA). 3-10 mg of sample
material was heated from 50 to 800 0C at a ramping rate of 10
0C/min under nitrogen gas atmosphere.
C. Ash Content
Ash contents were measured by combusting 5g of raw
materials in a muffle furnace at 8000
C for 4h.
D. Fourier Transform Infrared Spectroscopy (FT-IR)
The physico-chemical characteristics of activated carbon
produced by the optimum conditions in this experiment were
Utilization of Biodiesel Wastes as a Bioresource for the
Preparation of Activated Carbon
A. Buasri, N. Chaiyut, V. Loryuenyong, E. Phakdeepataraphan, S. Watpathomsub,
and V. Kunakemakorn, Member, IACSIT
International Journal of Applied Physics and Mathematics, Vol. 3, No. 3, May 2013
173DOI: 10.7763/IJAPM.2013.V3.200

2. determined. These surface functional groups were analyzed
by using a FT-IR spectroscopy (Nicolet Impact 410). The
activated carbon samples were mixed with potassium
bromide (KBr) and the mixture was pressed as a pellet prior
to analysis. The IR spectrum was obtained at a resolution of 4
cm-1
over the range of 400-4,000 cm-1
.
E. Optimum Conditions for Synthesis of Activated Carbon
Various parameters effecting activated carbon
performance including acidic treatment, impregnation ratio
of KOH to charcoal (1:1-2:1 w/w), activation temperature
(700-900 0C) and activation time (0-120 min) were studied.
In this work, efficiency and quality of the activated carbon
were preliminarily characterized by measuring both iodine
number and methylene blue number. Iodine number can be
used for the estimation of the relative surface area and the
measurement of porosity with the pores size greater than 1.0
nm in diameter. Methylene blue number, on the other hand, is
one of the most widely recognized probe molecules for
assessing the removal capacity of the specific carbon for
moderate-size pollutant molecules (≥1.5 nm).
F. Adsorption of Iodine and Methylene Blue
The iodine number of activated carbon was obtained on the
basis of the standard test method (ASTM D4607-94) by
titration with sodium thiosulphate (Na2S2O3). The
concentration of iodine solution was thus calculated from
total volume of Na2S2O3 used and volume dilution factor.
By batch experiment, methylene blue solution was mixed
with activated carbon and stirred at room temperature in the
place without light. After the completed reaction, the
solutions were filtered and the concentrations of methylene
blue solution were then determined by UV-Visible
Spectrophotometer from Jasco V-350 at 664 nm. The
equilibrium adsorption capacities (Qe) of the activated
carbon were determined based on adsorbate mass balance
using (1).
Qe = (Co - Ce)V/M (1)
where Co and Ce are the initial and equilibrium
concentrations of the dye (mg/L), respectively. V is the
volume of the aqueous solution (L) and M is the mass of
activated carbon used (g).
III. RESULTS AND DISCUSSION
A. Thermal Analysis of Materials
Fig. 1 shows TGA graphs of PS. It was found that the first
weight loss occurs at 50-1000
C due to the elimination of
moisture in the raw material. The large weight loss occurs at
the temperature of 4000
C due to the decomposition of the
major components of lignocellulosic biomass including
hemicellulose, cellulose and lignin. Lignin is generally the
first component to decompose at a low temperature and low
rate and continues on until approximately 9000
C.
Hemicellulose is a light fraction component which also
decomposes at the low temperature region between 200 and
3600
C. Cellulose is the last component to decompose at the
high temperature range of 240-3900
C. At the temperatures
above 4000
C, the final decomposition or weight loss involves
the aromatization process of lignin fraction leading to very
low weight loss [8]. Furthermore, it was found that the
residual weight of PS treated in HF (B) is lower than that
without HF treatment (A). This might be because HF
removes the ash from the raw material [9], [10].
Fig. 1. Thermogram of materials (A) PS (B) PS soaked in HF.
Fig. 2 shows TGA graphs of JS. The first weight loss at
50-100 0C is observed due to the release of moisture in the
raw material. At higher temperatures between 180-3200
C,a
gradual weight loss is due to the thermal degradation of
hemicellulose and cellulose. Moreover, this temperature also
was an initial step for carbon structure formation. The last
step of weight loss at 320-5500
C indicates the thermal
degradation of lignin. At the temperatures above 5500
C, no
further weight loss is observed, indicating the formation of
final carbon structures. Similar to PS, JS with HF soaking has
lower remaining weight after heating to high temperatures.
Fig. 2. Thermogram of materials (A) JS (B) JS soaked in HF.
B. Ash Content of Materials
To verify the ability of HF to remove the ash, both raw
materials were combusted in a furnace at 800 0C for 4 h. The
remaining ash contents are listed in Table I. From Table I,
when soaked the raw materials in HF, the amount of ash in
raw material was reducing. This confirms that HF can
remove the ash that might block activated carbon’s pore out
of the raw material.
C. Infrared Spectroscopy Analysis of Materials
The FTIR spectra of the raw materials and activated
carbons from PS (Fig. 3) and JS (Fig. 4) showed similar
peaks. The peaks at 2923 and 2855 cm-1
are ascribed to C-H
International Journal of Applied Physics and Mathematics, Vol. 3, No. 3, May 2013
174

3. aliphatic stretching [5], [11]. Other important absorption
peaks at 1022 cm-1
and 1100-1120 cm-1
represent C-O
stretching [9], [12] and aromatic skeleton of lignin [13],
respectively. Strong and broad peaks at 3300-3500 cm-1
correspond to O-H stretching [14]. The peaks of symmetrical
stretching of C=C are also observed at 1600-1700 cm-1
.
There is another peak at 1385 cm-1
due to the presence of
–CH3 stretching. It can be concluded that activation process
decreased the lignin and aliphatic chain in the raw materials
structure by thermal degradation, so the intensity of peak at
2923 and 2855 cm-1
, 1100-1120 and 1022 cm-1
were
decreased.
TABLE I: ASH CONTENT IN RAW MATERIALS
Raw
materials
Ash weight (g) Ash content (%)
Untreated Treated Untreated Treated
JS 0.2506 0.2067 5.012 4.134
PS 0.2605 0.1042 5.21 2.084
Fig. 3. IR-spectra of materials (A) PS (B) ACPS.
Fig. 4. IR-spectra of materials (A) JS (B) ACJS.
D. Adsorption Capacity of Materials
Fig. 5 shows the effects of HF treatment on adsorption
capacity of activated carbon. It was found that activated
carbons treated with HF have higher iodine and methylene
blue adsorption capacities than those without HF treatment.
Based on previous works, HF treatment could reduce ashes
that clog up activated carbons’ porosities [1], [9].
Fig. 6 shows the effects of impregnation ratio on
adsorption capacity. For activated carbon from PS, both
iodine number and methylene blue adsorption capacities
were found to increase with increasing impregnation ratio.
The higher impregnation ratio could result in an increasing
possibility of reaction between activating agent and PS, and
hence a larger amount of both micropores and mesopores [2],
[3], [9], [15].
For activated carbon from JS, it was found that the optimal
impregnation ratio with the highest iodine number and
methylene blue adsorption capacity is equal to 1 and 1.5,
respectively. At higher values than 1, the iodine number
starts to decrease, and this might be due to lower surface area
from the coalescence of micropores into mesopores [2], [6].
Similarly, for methylene blue adsorption capacity, too large
impregnation ratio could induce mesopore widening,
resulting in lower surface area [3].
= ACPS in I2 = ACJS in I2
= ACPS in MB = ACJS in MB
Fig. 5. Effect of soaking in HF on adsorption capacity of materials.
= ACPS in I2 = ACJS in I2
= ACPS in MB = ACJS in MB
Fig. 6. Effect of impregnation ratio on adsorption capacity of materials.
Fig. 7 shows the effects of activation temperature on
adsorption capacity. The iodine numbers of both raw
materials decrease with increasing temperatures. This is due
to the degradation of volatiles in the activated carbon,
causing the micropores to be widened into larger pores [1],
[16]. In contrast, for methylene blue adsorption capacity,
some of micropores could be converted to mesopores at
higher activation temperature, leading to an increase in
methylene blue adsorption capacity [2], [9].
Fig. 8 shows the effects of activation time on adsorption
capacity. The results of methylene blue adsorption test reveal
an increase in adsorption capacity with increasing activation
time. For the test of iodine number, it was found that
increasing activation time reduces adsorption capacity in
activated carbon from oil palm shell due to the pore widening
effects. For activated carbon from JS, it was found that
activation time of 1 h is the best time to maximize the iodine
International Journal of Applied Physics and Mathematics, Vol. 3, No. 3, May 2013
175

4. number. Longer reaction time could induce micropore to
mesopore conversion, reducing the iodine number [16], [17].
= ACPS in I2 = ACJS in I2
= ACPS in MB = ACJS in MB
Fig. 7. Effect of activation temperature on adsorption capacity of materials.
= ACPS in I2 = ACJS in I2
= ACPS in MB = ACJS in MB
Fig. 8. Effect of activation time on adsorption capacity of materials.
IV. CONCLUSION
In summary, this research shows that biodiesel wastes
could be effectively used for the preparation of activated
carbons. The suitable conditions to achieve optimum iodine
number for activated carbon from both PS and JS is 7000
C
activation temperature, 1 h activation time and 1:1
impregnation ratio. However, better adsorption capacity is
obtained with HF soaking for JS and without HF soaking for
PS.
ACKNOWLEDGMENT
The authors acknowledge sincerely the Department of
Materials Science and Engineering (MSE), Faculty of
Engineering and Industrial Technology, Silpakorn
University (SU) and National Center of Excellence for
Petroleum, Petrochemicals, and Advanced Materials
(PPAM), Chulalongkorn University (CU) for supporting and
encouraging this investigation.
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Achanai Buasri received his bachelor’s degree in
petrochemicals and polymeric materials from
Silpakorn University, Thailand in 2002 and master’s
degree in chemical engineering from Chulalongkorn
University, Thailand in 2004. He is presently working
as Assistant Professor in Department of Materials
Science and Engineering, Faculty of Engineering and
Industrial Technology, Silpakorn University, Thailand
and joined institute in 2004. In addition, he is working
as researcher in National Center of Excellence for Petroleum, Petrochemicals
and Advanced Materials, Chulalongkorn University, Thailand. His main
research interests are nanocomposite materials, renewable energy and
wastewater treatment. This author became a Member of IACSIT.
Nattawut Chaiyut received his bachelor’s degree in
petrochemicals and polymeric materials from
Silpakorn University, Thailand in 1999 and doctor of
philosophy (Ph.D.) degree in polymer science and
technology from Mahidol University, Thailand in
2005. He is presently working as Lecturer in
Department of Materials Science and Engineering,
Faculty of Engineering and Industrial Technology,
Silpakorn University, Thailand and joined institute in
Author’s formal
photo
International Journal of Applied Physics and Mathematics, Vol. 3, No. 3, May 2013
176

5. International Journal of Applied Physics and Mathematics, Vol. 3, No. 3, May 2013
177
2004. In addition, he is working as researcher in National Center of
Excellence for Petroleum, Petrochemicals and Advanced Materials,
Chulalongkorn University, Thailand. His main research interests are
biopolymers, polymer nanocomposites and polymer physics.
Vorrada Loryuenyong received her bachelor’s
degree in materials science and engineering from The
Pennsylvania State University, USA in 2000, master’s
degree in materials science and engineering from
University of California-Berkeley, USA in 2002 and
doctor of philosophy (Ph.D.) degree in materials
science and engineering from University of
California-Berkeley, USA in 2006. She is presently
working as Assistant Professor in Department of
Materials Science and Engineering, Faculty of Engineering and Industrial
Technology, Silpakorn University, Thailand and joined institute in 2006. In
addition, she is working as researcher in National Center of Excellence for
Petroleum, Petrochemicals and Advanced Materials, Chulalongkorn
University, Thailand. Her main research interests are sol-gel process,
semiconductor materials, thin film, photocatalysts and dye-sensitized solar
cell (DSSC).
Ekasit Phakdeepataraphan is an undergraduate
student in bachelor's degree program (petrochemicals
and polymeric materials) with the Department of
Materials Science and Engineering, Faculty of
Engineering and Industrial Technology, Silpakorn
University, Thailand.
Somchai Watpathomsub is an undergraduate student in
bachelor's degree program (petrochemicals and
polymeric materials) with the Department of Materials
Science and Engineering, Faculty of Engineering and
Industrial Technology, Silpakorn University, Thailand.
Vasin Kunakemakorn is an undergraduate student in
bachelor's degree program (petrochemicals and
polymeric materials) with the Department of Materials
Science and Engineering, Faculty of Engineering and
Industrial Technology, Silpakorn University,
Thailand.
Author’s formal
photo
Author’s formal
photo
Author’s formal
photo